Du X, Hamre K M
Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
Teratology. 2001 Dec;64(6):301-10. doi: 10.1002/tera.1085.
Previous studies have demonstrated that excessive prenatal alcohol exposure can damage the auditory and vestibular systems, in particular, cochlear hair cells. However, the direct effect of ethanol on the peripheral neurons in these pathways has not been examined. To study the effects of prenatal ethanol exposure on the developing vestibulocochlear ganglion (VCG) complex and the peripheral sensory organs, we exposed pregnant mice to ethanol and examined the levels of cell death in the inner ear.
Pregnant C57BL/6J mice were administered one of three doses of either ethanol (3.0, 4.5, and 5.5 g/kg) or isocaloric maltose/dextrin via intragastric intubation on gestational day (GD) 12.5. Embryos were dissected out of the uterus 8 hr after the intubation. Dying cells in the inner ear were stained with Nissl stain and labeled by in situ terminal dUTP nick-end labeling (TUNEL), and the percentage of dying cells was quantified.
Ethanol exposure produced region-specific effects, with ethanol-exposed embryos exhibiting enhanced cell death only in the VCG complex, and not in the primitive saccule, cochlea, semicircular canal, or endolymphatic sac. The effects of ethanol on cell death in the VCG are dose dependent, with a significant increase in the level of cell death found only at the higher doses.
Ethanol has a selective cytotoxic dose-dependent effect on the VCG at GD 12.5 suggesting that loss of VCG neurons may contribute to hearing and /or vestibular abnormalities in FAS children. Furthermore, the presence of TUNEL-positive cells and DNA laddering is consistent with the cells undergoing apoptotic cell death.
先前的研究表明，孕期过度暴露于酒精会损害听觉和前庭系统，尤其是耳蜗毛细胞。然而，乙醇对这些通路中周围神经元的直接影响尚未得到研究。为了研究孕期乙醇暴露对发育中的前庭蜗神经节（VCG）复合体和周围感觉器官的影响，我们将怀孕小鼠暴露于乙醇中，并检测内耳中的细胞死亡水平。
在妊娠第12.5天，通过胃内插管给怀孕的C57BL/6J小鼠给予三种剂量之一的乙醇（3.0、4.5和5.5 g/kg）或等热量的麦芽糖/糊精。插管后8小时从子宫中取出胚胎。内耳中的死亡细胞用尼氏染色法染色，并用原位末端脱氧尿苷三磷酸缺口末端标记法（TUNEL）进行标记，并对死亡细胞的百分比进行定量。
乙醇暴露产生了区域特异性影响，暴露于乙醇的胚胎仅在VCG复合体中表现出细胞死亡增加，而在原始球囊、耳蜗、半规管或内淋巴囊中没有增加。乙醇对VCG中细胞死亡的影响是剂量依赖性的，仅在较高剂量下发现细胞死亡水平显著增加。
乙醇在妊娠第12.5天对VCG具有选择性细胞毒性剂量依赖性作用，这表明VCG神经元的丧失可能导致胎儿酒精谱系障碍（FAS）儿童的听力和/或前庭异常。此外，TUNEL阳性细胞的存在和DNA梯状条带与细胞发生凋亡性细胞死亡一致。
